1. Field of the Invention
The present invention relates to control of a communications terminal, and more particularly, to control of additional functions in a mobile communications terminal.
2. Description of the Related Art
A communications terminal such as a mobile telephone, which is mainly intended for use through connection to a network of communication services, may have additional functions in addition to basic communications functions such voice calls, data communications and the like. For example, recent portable telephones equipped with multiple functions may have a wide variety of additional functions such as a digital camera function, a GPS function, a game function, a music reproducing function, a television receiving function and the like. These additional functions can be utilized without connecting the portable telephone to a mobile communications network, and have substantial value just being used as stand-alone features of the mobile telephone.
Generally, in mobile communication services, the fee charged to the user is kept low at the time when the user initially subscribes to the service, in order to promote the subscription. After subscribing to a mobile communication service, the user can purchase a low cost portable telephone and start the utilization. If the user cancels the contract immediately after he has subscribed to the mobile communication service and purchased a portable telephone, the portable telephone will be left in the user's possession.
By taking advantage of this situation, if the user cancels the contract immediately after he has subscribed to the mobile communication service, the user can still utilize additional functions of the portable telephone such as a digital camera function, a GPS function, a game function and the like even after the cancellation. Carriers do not regard this as the standard way in which a mobile phone should be used, and if such usage increases, carriers will increasingly incur more damage, resulting in disadvantages, such as an increase in charges, to users who use the portable phone in the way it which it was originally intended by the carriers, i.e. mainly for voice and data calls. This kind of bad predicament has occurred because some users are using the additional functions of the mobile phone independently of the carriers, i.e. they retain the phone and use the additional functions but have cancelled the service contracts with the carriers.
On the other hand, JP-A-7-162958 discloses a method of preventing a mobile terminal which does not have a service contract from being used. According to this method in which a timer measures the period of time that has elapsed after an update has been made, use of a mobile phone is made invalid if a fixed time had elapsed during which the timer has not been updated by a signal from a base station. In this way, it is possible to prevent the use of communications functions, including broadcasting, by a radio communications terminal which does not have a subscriptions contract. While the method disclosed in JP-A-7-162958 can invalidate communications functions, the user can still continue to utilize additional functions of the radio communications terminal.
Up to the present, the question of utilization of additional functions of the mobile phone by the user, after cancellation of the service contract, has not been sufficiently investigated, so that no effective means have been developed to prevent this. In addition, even portable telephones which have mobile communication service contracts, have not been provided with means for the user to select additional functions which can be used.